Two-piece cans are widely used in the beverage industry to package soft drinks, alcoholic drinks, and the like. These two-piece beverage cans typically include a thin-walled tubular body portion having a closed end and an open end. The open end is sealed by a can end once the can body has been filled with a liquid beverage.
Can bodies are produced from a metal sheet product, typically aluminum or steel. The aluminum or steel sheet arrives at the can manufacturing plant in very large coils. The sheet is fed continuously from an uncoiler or payoff reel into a cupping press which cuts out thousands of disks per minute and forms them into shallow cups. This is called the blank and draw process. Surplus material from the coil is recycled, and sold back to the material supplier.
The shallow cups are transported to a bodymaker where the can body begins to take its final shape. In the bodymaker, the shallow cup goes through a process called draw and iron or DI. During DI, the shallow cup is placed in front of a moving ram which forces it through a series of precision rings, each a little smaller than the previous one. This reduces the thickness of the metal (wall ironing) and, as a result, the can gets taller. At the end of the stroke the base is formed, and the can body is removed from the ram.
A trimmer shears material excess about the open end of the can body. This trimming process insures that the can body is the correct height, and that the rim about the open end is uniform and free of earring (misshapen metal). Again, the surplus material from this process is recycled.
The trimmed can bodies then pass through highly efficient washers to remove lubricants used during the forming process and to prepare the can body outer surface for coating and printing. Cans are then dried in a drier or oven.
Depending on customer and design requirements, the outer surface of the can bodies may be externally coated with a white or clear base coat at a base coater station.
The next step is a highly sophisticated decorator, which applies a design to the outer surface of the can body using up to six colors. All six colors are printed onto the can body in the same operation. A clear-coat over-varnish is sometimes added to the printed can bodies to give a glossy finish.
Next, the inner surface of each can body is sprayed with a coating. This special layer is to protect the product in the can from interaction with the metal of the can body.
The decorated can bodies are then passed through a necker/flanger which reduces the diameter of the open end of the can body. This gives the can bodies the characteristic neck shape. Here, the diameter of the top of the can is reduced or ‘necked-in’. The top of the can is flanged outwards to enable the can end to be seamed to the can body after the can bodies are filled with a liquid beverage.
The can bodies are quality tested at each stage of manufacture. At the final stage, the can body is put through a series of additional tests, including a light test and internal and external inspection cameras. Any defective can bodies are automatically rejected.
Finally, the cans are packed on to pallets which are then either sent to a warehouse for storage or transported directly to the beverage producer for filling.
The can ends or lids are produced in a separate process. Can end manufacture begins with a large coil of aluminum or steel. The metal sheet is fed through a shell press, which stamps out and forms the basic can end shell. The can end shell is an unfinished can end with no forming and no tab attached—just a flat disk with the outside diameter curled to accept a can body neck. Scrap metal from the coil is collected and recycled.
The shells are transferred to a balancer or manual rollover station where the orientation of the shell is reversed so that a public side is face down and the product side is face up.
A special type of sealant called compound is applied to the inside curl of the shell. This ensures a perfect curl when the finished can end is seamed on to can body. This process is called lining and is done at very high speed on a compound lining machine.
Again, the shells are transferred to a balancer or manual rollover station where the orientation of the shell is reversed. In this beverage can component process the product side is turned face down, and the public side is turned face up.
The final step in the can end process is converting the lined shell into a finished end. This is done in a conversion press. This process forms and scores the shell into a finished or substantially finished can end or lid, and attaches a tab to the can end. There can be eight or more separate stages, or progressions, involved in converting a shell into a finished end at the conversion press.
Typically, the conversion press also produces a strip of tabs from a narrow coil of aluminum or steel sheet which is fed into an integral tab die. There are typically thirteen to seventeen working stages involved in producing the can end tab.
At all stages of the can end production process, the ends are constantly scanned by cameras and sophisticated leak detection systems. Functional checks are performed by computer controlled equipment and are backed up by extensive visual checks. These tests are essential in confirming the integrity of the product before the ends are packed into paper sleeves and palletized for shipment.
The processes for producing the components of a two-piece beverage can, the can bodies, can ends, and can end tabs, all begin with a large coil of aluminum or steel sheet being fed from an uncoiler or payoff reel to a first two-piece beverage can component process. These coils may weigh between 8 to 15 tons or even more, and the receiving and handling costs associated with processing the coils is considerable. Because the coils are of a fixed, uniform width, scrap accumulation is significant, and can exceed 10% of the weight of the coil.
In addition, this scrap must be processed to transfer it from the plant. The scrap may be baled or compacted for transport. These processes are costly to run and maintain.
Moreover, the use of coils can slow down two-piece beverage can component manufacture as a new coil must be loaded onto the uncoiler or payoff reel when the old coil is spent.
Thus, there is a need for a method of forming two-piece beverage can components which reduces scrap accumulation and improves productivity.
The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior methods of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings.